JP2018048888A - Method of detecting fluorine-containing compound gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that can detect a trace quantity of fluorine-containing compound gas even at a lower heating temperature than before.SOLUTION: A detection method is characterized in that: fluorine-containing compound gas and solid metal oxides are brought into contact with each other for a reaction in a temperature range of 100-800°C, and the produced gas is detected. Particularly, the solid metal oxides can be SiOor WO. On the surfaces of these solid metal oxides, alkali metal fluorides or alkali metal hydroxides may be attached.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for detecting a fluorine-containing compound gas capable of detecting a trace amount of a fluorine-containing compound gas.

  Many fluorine-containing compound gases such as chlorofluorocarbons, perfluorocarbons and perfluorocompounds have high ozone depletion potential (ODP) and global warming potential (GWP). It has become. For this reason, alternative gases with low ODP and GWP have been developed, but these include many flammable or toxic gases.

  In the detection of these fluorine-containing compound gases, there are infrared-type sensors that use infrared absorption of fluorine-containing compound gases and heat-wire-type sensors that use the resistance change of a hot-wire coil, both of which have a detection limit of several hundred ppm, Detection of several ppm of fluorine-containing compound gas was impossible. In recent years, alternative gases with low ODP and GWP have contained many flammable or toxic gases, and these gases are required to be detected in minute amounts on the order of several ppm.

  As a method for detecting a trace amount of fluorine-containing compound gas on the order of several ppm, the present applicant converts the gas into a gas that is easy to detect by contact reaction with heated solid metal, and the gas is detected using electrolysis. A method for detecting a fluorine-containing compound gas is disclosed (Patent Document 1), wherein the detection is based on the output of a gas detector or a tape-type gas detector. Further, as a method for obtaining a necessary reaction rate even when the reaction temperature is further lowered, a method using the solid metal with an alkali metal fluoride added to the surface has been proposed (Patent Document 2). Further, as a method for uniformly maintaining the surface adhering material for a long period of time, it has been proposed that the adhering material is an alkali metal hydroxide or a metal oxide (Patent Document 3).

Japanese Patent No. 3375072 Japanese Patent No. 3640601 JP 2003-139760 A

  However, in the method for detecting a fluorine-containing compound gas, when the solid drug in which an alkali metal fluoride or the like is attached to a solid metal is used, a necessary reaction rate can be obtained even when the reaction temperature is lowered, but 400 ° C. About high temperature heating is required (Patent Documents 2 and 3). For this reason, the heating device becomes large, and the material of the heating device is limited to that which is durable at this temperature. Moreover, since the power consumption increases, the running cost also increases. The present invention has been made paying attention to such a point, and an object thereof is to provide a method capable of detecting a trace amount of a fluorine-containing compound gas even when the heating temperature for causing the reaction is lowered.

  As a result of intensive studies on the above problems, the present inventor causes a reaction for detecting a trace amount of a fluorine-containing compound gas by reacting a fluorine-containing compound gas with a solid metal oxide instead of a solid metal. It has been found that the heating temperature is lowered. Furthermore, in the said reaction, it discovered that it was effective to attach an alkali metal fluoride or an alkali metal oxide to the metal oxide surface, and reached | attained this invention.

  That is, the present invention provides a method for detecting a fluorine-containing compound gas, which comprises reacting a fluorine-containing compound gas with a solid metal oxide in a temperature range of 100 to 800 ° C. to detect the generated gas. .

  The present invention can provide a method capable of detecting a trace amount of a fluorine-containing compound gas even at a heating temperature lower than that of the prior art.

It is the schematic of the experimental apparatus for the detection confirmation of fluorine-containing compound gas.

Hereinafter, the present invention will be described in detail.
In the method for detecting a fluorine-containing compound gas according to the present invention, a solid metal oxide or an alkali metal oxide or alkali metal fluoride added thereto is added to a gas containing a trace amount of a fluorine-containing compound gas at 100 to 800 ° C. The method includes a step of performing a contact reaction in a temperature range, and a step of detecting a gas generated by the reaction.

The fluorine-containing compound gas to be detected is chlorofluorocarbon, perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, perfluoro compounds, etc., and in particular, C ₅ F ₈ , C ₄ F ₈ , C ₄ F ₆ , _{C 2 F 6, C 3 F} 8, CF 4, C 5 HF 7, CH 2 F 2, CHF 3, CCl 3 F, CCl 2 F 2, CClF 3, CCl 4, CHClF 2, CH 3 Cl, CH 3 Br, CHCl ₃ , CBr ₂ F ₂ , CBrF ₃ , CH ₂ Br ₂ , CH ₂ BrCl, CBr ₃ F, CHBr ₂ F, CHBrF ₂ , CBrClF ₂ , C ₂ H ₃ Cl, C ₂ BrF ₅ , C ₂ ClF ₅ , C ₂ Cl ₂ F ₄ , C ₂ Cl ₃ F ₃ , C ₂ BrF ₄ , C ₂ Br ₂ F ₄ , C ₂ H _{2 Br 2 F 4, C 2} Br 2 ClF 3, a NF _3. With respect to the gas targeted by the detection method of the present invention, the trace amount is a gas concentration in which the fluorine-containing compound gas is several thousand volume ppm or less, particularly a gas having a concentration range of 1 ppb or more and 1000 ppm or less. In particular, when C ₅ F ₈ is the target of detection, since the exposure allowable concentration is 2 ppm by volume, it is preferable that detection can be performed well in a concentration range of 0.01 volume ppm or more and 20 volume ppm or less, and 0.1 volume. More preferably, it can be satisfactorily detected in a concentration range of not less than ppm and not more than 10 volume ppm.

In the present invention, the fluorine-containing compound gas and the solid metal oxide are contact-reacted in a heated state, and converted into a gas such as SiF ₄ or WF ₆ that is a gas that is easier to detect gas. An alkali metal fluoride or an alkali metal hydroxide may be attached to the surface of the solid metal oxide.

The solid metal oxide used in the present invention is at least one selected from the group consisting of silicon oxide and tungsten oxide. Examples of silicon oxide include SiO ₂ , and examples of tungsten oxide include WO ₃ . be able to. In addition, as the additive, the alkali metal fluoride is sodium fluoride or potassium fluoride, and the alkali metal hydroxide is sodium hydroxide or potassium hydroxide. By adding these, the solid metal oxide reacts with the fluorine-containing compound gas at a lower temperature.

  In the present invention, the external shape of the solid metal oxide is spherical or crushed. The surface state is not particularly limited, but a porous or roughened surface having a large surface area is desirable. The purity of the solid metal oxide is not particularly limited, but is preferably 90% by mass or more, more preferably 98% by mass or more, and further preferably 99% by mass or more.

  The size of the solid metal oxide was such that it passed through a sieve with an opening of 9.5 mm and did not pass through a sieve with an opening of 0.5 mm. Large ones that do not pass through a sieve with a mesh opening of 9.5 mm have a problem that the filling space becomes large, a large amount of gas to be detected is required, and the reaction becomes insufficient due to a decrease in the contact area with the gas. Therefore it is not suitable. Moreover, what passed through the sieve having an opening of 0.5 mm is not suitable because it blocks the flow of the gas to be measured and inhibits the flow.

When C ₅ F ₈ gas is used as the fluorine-containing compound gas and it is brought into contact with SiO ₂ that is a solid metal oxide at 280 ± 50 ° C. in the presence of oxygen, it is a gas to be measured that is easy to detect, such as the formula (1) Some SiF ₄ is obtained. Similar reactions are believed to occur in the temperature range of 100-800 ° C.
_{C 5 F 8 + 2SiO 2 +} 3O 2 → 2SiF 4 + 5CO 2 (1)

When an alkali metal hydroxide is used as the attachment, the alkali metal hydroxides NaOH, KOH, etc. produce various metal fluorides by reaction with the fluorine-containing compound gas. For example, when C ₅ F ₈ gas is used for the fluorine-containing compound gas and NaOH is used for the alkali metal oxide, a reaction represented by the formula (2) is obtained at 300 ± 50 ° C. in the presence of oxygen.
C ₅ F ₈ + 8NaOH + 3O ₂ → 8NaF + 4H ₂ O + 5CO ₂ (2)
As for the NaF produced here, when SiO ₂ is used as the solid metal oxide, SiF ₄ is produced at 300 ± 50 ° C. in the presence of moisture as shown in the equation (3).
4NaF + SiO ₂ + 2H ₂ O → SiF ₄ + 4NaOH (3)

When an alkali metal fluoride is used as an attachment, a treatment is required in advance. For example, when NaF is used for the alkali metal fluoride and SiO ₂ is used for the solid metal oxide, SiF ₄ is generated as shown in the formula (3) at 300 ± 50 ° C. in the presence of moisture and oxygen. The As the SiF ₄ is formed, the NaF is replaced with NaOH. Until this is completed, it is necessary to discharge the SiF ₄ out of the system in advance. However, after the replacement, the detection of the fluorine-containing compound gas is performed from (2) to (3 The reaction mechanism is the same as that in the formula. As described _above, in processing the C 5 _{F 8} gas, a solid metal oxide 200 to 500 ° C., preferably 250 to 400 ° C., it is preferably heated and more preferably to 300 to 380 ° C..

FIG. 1 shows a schematic diagram of an experimental apparatus for detecting and confirming a fluorine-containing compound gas according to the method of the present invention. The sample gas filling container 1 is filled with a gas containing a trace amount of a fluorine-containing compound to be detected in the atmosphere. The filling cylinder 2 is filled with a solid metal oxide, a solid metal, or an alkali metal fluoride or an alkali metal hydroxide impregnated therein, and the gas in the sample gas filling container is filled into the filling cylinder at 500 cm / min. Introduce about ³ and contact with the filling. The filling cylinder 2 is heated by the heater 3 to heat the filling inside the filling cylinder. However, since the heating temperature is lowered by the gas flow, a temperature higher than the above reaction temperature is necessary to confirm the detection of the fluorine-containing compound gas. From the outlet of the filling cylinder 2, it is introduced into a gas detector 4 using electrolysis or a tape-type gas detector 5, and an electric output necessary for detection is obtained by these gas detectors.

In the gas detector 4 using electrolysis, a gas such as SiF ₄ or WF _{6 is} electrolyzed on the electrode, and the fluorine-containing compound gas can be detected by the electric output generated at that time. Further, in the tape type gas detector 5 which is another method of the gas detector, a gas such as SiF ₄ or WF ₆ is applied to an air permeable tape made of a material such as nitrocellulose impregnated with a color former. The reflected light from the color developed by the reaction is converted into electrical output, and the fluorine-containing compound gas is detected.

  Hereinafter, although it demonstrates concretely by an Example, it is not limited to this Example. Examples and comparative examples are summarized in Tables 1 and 2.

[Example 1]
The atmosphere of C ₅ F ₈ = 10 ppm by volume was used as the detection target gas, and spherical porous SiO ₂ was used as the solid metal oxide. The size of the solid metal oxide was that which passed through a sieve having an aperture of 2.0 mm and did not pass through a sieve having an aperture of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C.
After introducing the gas to be detected, detection was confirmed in a gas detector using electrolysis and a tape-type gas detector based on the components of the gas generated by the reaction with the solid metal oxide as shown in Table 1 (Table 1). (Indicated with a circle).

[Examples 2-35]
In the same manner as in Example 1, various detection target gases were changed and measurement was performed. The concentration of the detection target gas was 10 ppm by volume in the atmosphere. As shown in Table 1, the measurement results for each detection target gas were confirmed in the gas detector using electrolysis and the tape-type gas detector even when the type of detection target gas was changed.

[Example 36]
In the same manner as in Example 1, the measurement was performed using porous WO ₃ having a spherical shape instead of SiO _{2 as} the metal solid oxide. As a result, even if the type of metal oxide was changed as shown in Table 1, detection was confirmed in a gas detector using electrolysis and a tape-type gas detector.

[Examples 37 to 40]
In the same manner as in Example 1., NaF as the impregnating material to the solid metal oxide surface is an alkali metal fluoride, KF, NaOH is an alkali metal hydroxide, using KOH, in a weight ratio to the SiO ₂ The measurement was carried out by attaching to 1000 ppm. The filling tube heating temperature was 330 ° C. As shown in Table 1, it was confirmed that the measurement results by the attachments were detected in a gas detector using electrolysis and a tape-type gas detector.

[Comparative Example 1]
In the same manner as in Example 1, Si that was a solid metal was used instead of SiO ₂ that was a solid metal oxide. The size of the solid metal was that which passed through a sieve having an opening of 2.0 mm and did not pass through a sieve having an opening of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C. as in Example 1.
After introducing the detection target gas, detection was not confirmed in the gas detector using electrolysis and the tape type gas detector due to the components of the gas generated by the reaction with the solid metal as shown in Table 2 (in Table 2) (Indicated by ×).

[Comparative Examples 2-3]
In the same manner as in Comparative Example 1, the detection target gas was measured as C ₄ F ₆ and C ₅ HF ₇ . The concentration of the detection target gas was 10 ppm by volume in the atmosphere. The heating temperature of the filling cylinder was 350 ° C. as in Examples 3 and 7. As shown in Table 1, the measurement results for each detection target gas were not detected in the gas detector using electrolysis and the tape-type gas detector even when the type of detection target gas was changed.

[Comparative Example 4]
In the same manner as in Comparative Example 1, W was used instead of Si, which is a solid metal. The size of the solid metal was that which passed through a sieve having an opening of 2.0 mm and did not pass through a sieve having an opening of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C. as in Example 35.
After introducing the detection target gas, detection was not confirmed in the gas detector using electrolysis and the tape-type gas detector due to the components of the gas generated by the reaction with the solid metal as shown in Table 1 (in Table 2) (Indicated by ×).

[Comparative Examples 5-6]
In the same manner as in Comparative Example 1, NaF, which is an alkali metal fluoride, and NaOH, which is an alkali metal hydroxide, are used as the adhering material on the surface of the solid metal. The measurement was carried out. The filling tube heating temperature was 330 ° C. as in Examples 37 to 40. As shown in Table 1, no detection was confirmed in the gas detector using electrolysis and the tape-type gas detector.

When Example 1 and Comparative Example 1 are compared, in the detection of the same fluorine-containing compound gas, the solid metal in the filling cylinder that reacts with the gas is a solid metal oxide, so that the gas necessary for the detection of the gas can be obtained. The heating temperature of the filling cylinder could be lowered. This is considered to be because the gas or the gas generated from the gas has a higher reaction rate with the solid metal oxide than the solid metal and the heating temperature can be lowered.
As described in detail above, according to the method of the present invention, in the method for detecting a fluorine-containing compound gas, a gas containing a trace amount of the fluorine-containing compound gas is contacted with a heated solid metal oxide to detect the generated gas. Thus, it can be detected at a low heating temperature.

  According to the present invention, for example, a fluorine-containing compound gas used in a semiconductor element manufacturing process can be detected even in a trace amount when leaked from an apparatus or mixed in an outlet gas of an exhaust gas treatment apparatus. It prevents exposure of gas to workers and release to the atmosphere.

DESCRIPTION OF SYMBOLS 1 ... Sample gas (fluorine-containing compound gas) filling container 2 ... Filling cylinder 3 ... Filling cylinder heater 4 ... Gas detector 5 using electrolysis ... Tape type gas detector

Claims (7)

  A method for detecting a fluorine-containing compound gas, comprising: reacting a fluorine-containing compound gas with a solid metal oxide in a temperature range of 100 to 800 ° C. to detect the generated gas.   The method for detecting a fluorine-containing compound gas according to claim 1, wherein the solid metal oxide is at least one selected from the group consisting of silicon oxide and tungsten oxide. The method for detecting a fluorine-containing compound gas according to claim 2, wherein the silicon oxide is SiO ₂ and the tungsten oxide is WO ₃ .   The fluorine-containing material according to claim 1, wherein at least one selected from the group consisting of an alkali metal fluoride and an alkali metal hydroxide is attached to the surface of the solid metal oxide. Compound gas detection method.   The method for detecting a fluorine-containing compound gas according to claim 4, wherein the alkali metal fluoride is at least one selected from the group consisting of NaF and KF.   The method for detecting a fluorine-containing compound gas according to claim 4, wherein the alkali metal hydroxide is at least one selected from the group consisting of NaOH and KOH. The said temperature range is 200-500 degreeC, The detection method of the fluorine-containing compound gas of any one of Claims 1-6 characterized by the above-mentioned.

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